I expect as your car is a 1993 it has the Volvoguard I system with the triangular receiver on the windscreen. Worth a look at this link for some more detailed troubleshooting tips but assuming it is the relay in the 211/210 box that has gone faulty your quick fix might be to find the 211/210 box and connect some wire between pins 50E and 50F to bypass the immobiliser function. If you then put the relay back in position you should still have remote central locking and the alarm, just no immobiliser. This will not work if your problem is due to a wiring fault or something downstream of the immobiliser relay.
http://www.volvotips.com/index.php/8...ervice-manual/